1. Field of the Invention
The present invention generally relates to an apparatus and method for use in a wellbore. More particularly, the invention relates to a disconnect for separating two or more components in a wellbore.
2. Description of the Related Art
In the drilling, completion, and operation of a hydrocarbon wells, various wellbore components are inserted and removed from a previously drilled wellbore on a lower end of a tubular string. Wellbore components include packers (to seal off production zones), motors, pumps, sensors, sliding sleeves (to control flow of fluid in and out of production tubing), hydraulically set liners (for lining during cementing of casing), whipstocks (to divert drill bit while drilling), valves, cement shoe assemblies, and drill bits.
As wellbore components are delivered and removed from a wellbore, the components or the tubular string they are attached to can become stuck in the wellbore. The problem is exacerbated by non-liner wellbores or previously existing obstructions in the wellbore. In one example, a drill bit on an end of a drill string is used to increase the depth of the wellbore. As the drill rotates at the end of the string, it may become stuck or otherwise jammed in the wellbore. There are conventional wellbore devices that are designed to aid in freeing a component that is stuck in the wellbore. For example, a “jar” can be disposed in the drill string to selectively provide a jarring force to the stuck component. A jar includes a telescopic portion that permits axial elongation of the jar. By operating a jar that is disposed near the stuck component, a force can be developed to possibly free the component.
In other instances, the use of jars is inadequate to free a stuck component and the component must be exposed in the wellbore in order to remove it with the use of fishing tools. To permit a drill sting or other tubular string to be separated from a stuck component, disconnect devices, are placed at intervals in the drill string. A disconnect is a component that can be selectively separated into two portions. For example, a disconnect disposed in a string of tubulars can permit the string to be separated and the lower part left in the wellbore for accessibility by fishing tools. Likewise, a disconnect disposed between the end of a tubular string and a wellbore component, like a drill bit, permits the selective removal of the string of tubulars if the bit should become stuck.
Conventional pull type disconnects utilize shear pins to temporarily couple a first and second portion of the disconnect together or to hold an internal piston in a first position. Shear pins are designed to fail when they are subjected to a force, such as a tensile or compressive force developed across the pins. When a wellbore component is stuck and a disconnect is disposed in a tubular string near the component, an upward force applied from the surface can cause the shear pins of the disconnect to fail, permitting the string to be removed from the wellbore. After the tubular string is retrieved to the surface, a fishing tool is used to manipulate the stuck wellbore component.
Shear pins are sized and numbered based upon the shear force needed to operate a disconnect. While they have been used as temporary connections in wellbores for years, shear pins have limitations. For example, forces other than the intended force may prematurely cause the shear pins to shear, thus making them unreliable. Because the shear pins can shear prematurely, additional fishing operations may be required to retrieve the prematurely disconnected wellbore component, leading to lost production time. For example, shear pins located on a tubular string that includes a perforating gun can shear prematurely from the force generated when the perforating gun is fired. Additionally, shear pins can shear prematurely when a slide hammer bangs on a shifting tool in order to shift the sliding sleeve or when a jarring device is used to dislodge a component.
Therefore, there is a need for a more reliable disconnect for use in a wellbore. There is a further need for a disconnect that can operate only when a predetermined amount of tension force is applied to a member.